1. Field of the Invention
The present invention relates to a method and apparatus for analyzing the quantity of a chemical substance as well as for enumerating the quantity of blood cells present in a predetermined blood volume.
2. Description of the Prior Art
Prior art blood cell counting methods and apparatus utilized in accomplishing such methods primarily all require movement of a blood sample through a constricted passageway in what is commonly termed the electrolyte counting method or by utilizing the detection and measurement of blood cell count at a scattering angle. One such constricted passageway blood cell counting procedure is disclosed in U.S. Pat. No. 2,656,508 wherein a diluted specimen of particles suspended in a fluid flows past a constricted current passage through which a current is passing. The flow of fluid through the constricted area changes the conductivity of that area and causes the individual particles to modulate the current, passing through the electrodes in a sequential detectable manner, the cells being counted one at a time. Similarly, U.S. Pat. Nos. 3,549,994; 3,657,725; 3,654,439 and 3,412,254 are exemplary of prior art blood cell counting devices which count the particles or cells by means of light interruption by the particle in a constricted passageway for advancing a counter one-by-one. Another such prior art device is disclosed in U.S. Pat. No. 2,875,666 wherein both red and white blood cells are counted simultaneously. However, in this instance, the red and white blood cells are stained and are then passed through a constricted passageway one-by-one so as to be sequentially counted in this fashion by means of subjecting the constricted passageway to a colored light source which comprises both the color to be absorbed by the cells being detected and the color to be transmitted. This light is filtered with a filter having a wavelength which corresponds to the light being absorbed by the cells being detected and the decrease in intensity of the light passing through the filter actuates a photocell which corresponds to the amount of cells passing through the constricted passageway in substantially successive or sequential fashion. However, these prior art devices are time consuming due to the quantity of time required to count the cells in successive or sequential fashion as opposed to being able to detect the overall quantity of blood cells in a given blood sample simultaneously with one measurement rather than a plurality of successive measurements. This time factor becomes particularly critical when a large number of samples are being tested such as in a hospital environment or a clinical testing laboratory. Furthermore, special types of tubes having such a constricted passageway of specified dimensions must be constructed and these special tubes increase the cost of the instrumentation.
In addition, prior art counting methods have not proved satisfactory with respect to the counting of leucocytes in that considerable effort must be expended so as to ensure that the leucocyte count is obtained substantially free of erythrocytes and other chemical constituents of the blood. Furthermore, users of such analyzers or blood cell counting instrumentation are normally also interested in determining the quantity of various chemical constituents, such as bilirubin, cholesterol, urea nitrogen, protein, glucose, cyanmethemoglobin, etc., of the blood, such as of the individual whose blood cell count is being determined. This is particularly so when such blood analysis is performed by a clinical testing laboratory or a hospital doing a complete blood test on a patient. Prior art methods and devices require the use of a separate chemical analyzer for determining the quantity of such chemical constituents in the blood, the requirement of an additional device in addition to the blood cell counting analyzer substantially increasing the cost of such instrumentation as well as being inefficient. Such chemical analyzer instrumentation may be of the type utilizing a colorimeter which produces an analog signal from the output of a photoelectric device, the amplitude of which signal is representative of a particular chemical substance sensed by a light filter. Such devices, however, to date have not been utilized in blood cell count analysis so as to provide a single instrument capable of providing both a blood cell count as well as an analysis of the chemical constituency of a blood sample. These disadvantages of the prior art are overcome by the present invention.